WASHINGTON (Reuters) - U.S. President Donald Trump on Tuesday continued to blast the investigation into alleged Russian meddling into last year's U.S. election, slamming his attorney general for not investigating his presidential rival in the race and raising questions, without offering evidence, about Ukraine's role.

In a pair of early morning tweets, Trump said U.S. Attorney General Jeff Sessions had "taken a very weak position" toward former Democratic presidential nominee Hillary Clinton and cited "Ukrainian efforts to sabotage Trump campaign - quietly working to boost Clinton'."

Ukrainian efforts to sabotage Trump campaign - "quietly working to boost Clinton." So where is the investigation A.G. @seanhannity

U.S. Attorney General Jeff Sessions (R) joins President Donald Trump (L) for an opioid and drug abuse listening session at the White House in Washington, U.S. March 29, 2017. REUTERS/Jonathan Ernst

President Donald Trump speaks with Attorney General Jeff Sessions as they attend the National Peace Officers Memorial Service on the West Lawn of the U.S. Capitol in Washington, U.S., May 15, 2017. REUTERS/Kevin Lamarque

U.S. Senator Jeff Sessions speaks next to U.S. Republican presidential candidate Donald Trump at a rally at Madison City Schools Stadium in Madison, Alabama February 28, 2016. REUTERS/Marvin Gentry

U.S. President Donald Trump watches as Vice President Mike Pence (R) swears in Jeff Sessions (L) as U.S. Attorney General while his wife Mary Sessions holds the Bible in the Oval Office of the White House in Washington February 9, 2017. REUTERS/Kevin Lamarque

UNITED STATES - FEBRUARY 28: Sen. Jeff Sessions, R-Ala., left, endorses Donald Trump to be the Republican nominee for president during a campaign rally at Madison City Schools Stadium in Madison, Ala., February 28, 2016. (Photo By Tom Williams/CQ Roll Call)

U.S. President Donald Trump congratulates Jeff Sessions after he was sworn in as U.S. Attorney General as his wife Mary Sessions looks on during a ceremony in the Oval Office of the White House in Washington, U.S., February 9, 2017. REUTERS/Kevin Lamarque

Republican presidential nominee Donald Trump sits with U.S. Senator Jeff Sessions (R-AL) (L) and retired U.S. Army General Keith Kellogg (R) during a national security meeting with advisors at Trump Tower in Manhattan, New York, U.S., October 7, 2016. REUTERS/Mike Segar

U.S. President Donald Trump speaks during a swearing-in ceremony for new Attorney General Jeff Sessions (R) at the White House in Washington, U.S., February 9, 2017. REUTERS/Kevin Lamarque

Under a portrait of former President Andrew Jackson, U.S. President Donald Trump (L) congratulates Jeff Sessions after he was sworn in as U.S. Attorney General during a ceremony in the Oval Office of the White House in Washington, U.S., February 9, 2017. REUTERS/Kevin Lamarque

President Donald Trump reaches out toward Attorney General Jeff Sessions as they attend the National Peace Officers Memorial Service on the West Lawn of the U.S. Capitol in Washington, U.S., May 15, 2017. REUTERS/Kevin Lamarque

US President-elect Donald Trump (C) talks with Alabama Governor Robert Bentley (2nd L) and US Attorney General nominee Jeff Sessions (L) as he arrives in Mobile, Alabama, for a 'Thank You Tour 2016' rally on December 17, 2016. / AFP / JIM WATSON (Photo credit should read JIM WATSON/AFP/Getty Images)

MOBILE, AL - DECEMBER 17: President-elect Donald Trump greets Senator Jeff Sessions, Trump's picks for attorney general, during a thank you rally in Ladd-Peebles Stadium on December 17, 2016 in Mobile, Alabama. President-elect Trump has been visiting several states that he won, to thank people for their support during the U.S. election. (Photo by Mark Wallheiser/Getty Images)

U.S. President Donald Trump watches as Vice President Mike Pence (R) swears in Jeff Sessions (L) as U.S. Attorney General while his wife Mary Sessions holds the Bible in the Oval Office of the White House in Washington, U.S., February 9, 2017. REUTERS/Kevin Lamarque

U.S. President Donald Trump congratulates Jeff Sessions after he was sworn in as U.S. Attorney General as his wife Mary Sessions looks on during a ceremony in the Oval Office of the White House in Washington, U.S., February 9, 2017. REUTERS/Kevin Lamarque